I see this offense being in a definite transition this year. Don't get me wrong, relying heavily on a FB and playing out of a ball control style of offense has reaped benefits for us in the past, I think it's outlived it's benefits.
Every time Bruce Miller lines up in the back field that means that Stevie Johnson, Bruce Ellington, Brandon Lloyd will be sitting on the sidelines. Hear me out on this one! For the first time in many years, our receiving core is the strength of our offense. Not utilizing as many as we can is compromising our strength!!!!
I guarantee you that if you line up Crabtree/Boldin/Johnson as our Wide Outs and pair them with Vernon Davis (coupled with Colin Kaepernick's ability to scramble) there is NO WAY that he defenses can load the box. From the onset of the play they'll be back peddling and spread thin trying to cover these guys.
This alone will create some massive running lanes. There is simply no reason why our Running Backs cannot operate in single back formations. The holes will be there. Trust me. Other teams run plenty of single back schemes, why can't we?
Obviously this all changes when we are in a short yardage run situation but aside from that, we have outgrown our need for a full time FB.